Tourmaline (Chemical equation NaR3Al6[Si6O18][BO3]3(OH,F)4) belongs to the trigonal crystal system and occurs as long, slender to thick prismatic and columnar crystals that are usually triangular in cross-section, vitreous luster, resinous luster in sections, It is transparent to translucent and non cleavage with 7.0 - 7.5 Mohs hardness range and Specific gravity range from 2.98 to 3.20, Tourmaline shows pyroelectricity in addition to the piezoelectric, the tourmaline can generate negative air ions spontaneously and emit far infrared rays due to It's unique polar crystal structure.
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